Meiosis must be an extremely accurate process because aneuploidy has severe consequences for the embryo and is often lethal. The goal of the project is to gain a greater understanding of meiotic chromosome segregation by identifying and characterizing additional gene products involved in meiosis. The model used is female meiosis in the fruit fly, Drosophila melanogaster, which has many features in common with human meiosis, and has the added advantage of being a well-developed genetic system. A new meiotic mutant, E(DTW), was identified in a screen for second-site dominant modifiers of the dominant meiotic phenotype of nodDTW, an allele of a gene encoding a kinesin-like protein. E(DTW) is a dominant enhancer of nodDTW and a recessive meiotic mutation that affects nonexchange chromosomes. Experiments are proposed to further characterize the genetic and cytological phenotypes of E(DTW), and to recover additional alleles in order to clone the locus, in an effort to understand its role in the meiotic machinery. At the conclusion of the proposed research, a new gene that plays a role in meiosis will have been characterized, as part of a continuing study of chromosome segregation.